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[89.240.117.139]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c3e551119fsm93658985a.108.2025.03.06.06.10.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Mar 2025 06:10:52 -0800 (PST) From: Juri Lelli To: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Waiman Long , Tejun Heo , Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Qais Yousef , Sebastian Andrzej Siewior , Swapnil Sapkal , Shrikanth Hegde , Phil Auld , luca.abeni@santannapisa.it, tommaso.cucinotta@santannapisa.it, Jon Hunter Subject: [PATCH v2 3/8] sched/deadline: Generalize unique visiting of root domains Date: Thu, 6 Mar 2025 14:10:11 +0000 Message-ID: <20250306141016.268313-4-juri.lelli@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250306141016.268313-1-juri.lelli@redhat.com> References: <20250306141016.268313-1-juri.lelli@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Bandwidth checks and updates that work on root domains currently employ a cookie mechanism for efficiency. This mechanism is very much tied to when root domains are first created and initialized. Generalize the cookie mechanism so that it can be used also later at runtime while updating root domains. Also, additionally guard it with sched_domains_mutex, since domains need to be stable while updating them (and it will be required for further dynamic changes). Reported-by: Jon Hunter Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow earlier for = hotplug") Signed-off-by: Juri Lelli --- include/linux/sched/deadline.h | 3 +++ kernel/sched/deadline.c | 23 +++++++++++++---------- kernel/sched/rt.c | 2 ++ kernel/sched/sched.h | 2 +- kernel/sched/topology.c | 2 +- 5 files changed, 20 insertions(+), 12 deletions(-) diff --git a/include/linux/sched/deadline.h b/include/linux/sched/deadline.h index 3a912ab42bb5..6ec578600b24 100644 --- a/include/linux/sched/deadline.h +++ b/include/linux/sched/deadline.h @@ -37,4 +37,7 @@ extern void dl_clear_root_domain(struct root_domain *rd); =20 #endif /* CONFIG_SMP */ =20 +extern u64 dl_cookie; +extern bool dl_bw_visited(int cpu, u64 cookie); + #endif /* _LINUX_SCHED_DEADLINE_H */ diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index ab565a151355..339434271cba 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -166,14 +166,14 @@ static inline unsigned long dl_bw_capacity(int i) } } =20 -static inline bool dl_bw_visited(int cpu, u64 gen) +static inline bool dl_bw_visited(int cpu, u64 cookie) { struct root_domain *rd =3D cpu_rq(cpu)->rd; =20 - if (rd->visit_gen =3D=3D gen) + if (rd->visit_cookie =3D=3D cookie) return true; =20 - rd->visit_gen =3D gen; + rd->visit_cookie =3D cookie; return false; } =20 @@ -207,7 +207,7 @@ static inline unsigned long dl_bw_capacity(int i) return SCHED_CAPACITY_SCALE; } =20 -static inline bool dl_bw_visited(int cpu, u64 gen) +static inline bool dl_bw_visited(int cpu, u64 cookie) { return false; } @@ -3171,15 +3171,18 @@ DEFINE_SCHED_CLASS(dl) =3D { #endif }; =20 -/* Used for dl_bw check and update, used under sched_rt_handler()::mutex */ -static u64 dl_generation; +/* + * Used for dl_bw check and update, used under sched_rt_handler()::mutex a= nd + * sched_domains_mutex. + */ +u64 dl_cookie; =20 int sched_dl_global_validate(void) { u64 runtime =3D global_rt_runtime(); u64 period =3D global_rt_period(); u64 new_bw =3D to_ratio(period, runtime); - u64 gen =3D ++dl_generation; + u64 cookie =3D ++dl_cookie; struct dl_bw *dl_b; int cpu, cpus, ret =3D 0; unsigned long flags; @@ -3192,7 +3195,7 @@ int sched_dl_global_validate(void) for_each_possible_cpu(cpu) { rcu_read_lock_sched(); =20 - if (dl_bw_visited(cpu, gen)) + if (dl_bw_visited(cpu, cookie)) goto next; =20 dl_b =3D dl_bw_of(cpu); @@ -3229,7 +3232,7 @@ static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq) void sched_dl_do_global(void) { u64 new_bw =3D -1; - u64 gen =3D ++dl_generation; + u64 cookie =3D ++dl_cookie; struct dl_bw *dl_b; int cpu; unsigned long flags; @@ -3240,7 +3243,7 @@ void sched_dl_do_global(void) for_each_possible_cpu(cpu) { rcu_read_lock_sched(); =20 - if (dl_bw_visited(cpu, gen)) { + if (dl_bw_visited(cpu, cookie)) { rcu_read_unlock_sched(); continue; } diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 4b8e33c615b1..8cebe71d2bb1 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2910,6 +2910,7 @@ static int sched_rt_handler(const struct ctl_table *t= able, int write, void *buff int ret; =20 mutex_lock(&mutex); + sched_domains_mutex_lock(); old_period =3D sysctl_sched_rt_period; old_runtime =3D sysctl_sched_rt_runtime; =20 @@ -2936,6 +2937,7 @@ static int sched_rt_handler(const struct ctl_table *t= able, int write, void *buff sysctl_sched_rt_period =3D old_period; sysctl_sched_rt_runtime =3D old_runtime; } + sched_domains_mutex_unlock(); mutex_unlock(&mutex); =20 return ret; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c8512a9fb022..c978abe38c07 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -998,7 +998,7 @@ struct root_domain { * Also, some corner cases, like 'wrap around' is dangerous, but given * that u64 is 'big enough'. So that shouldn't be a concern. */ - u64 visit_gen; + u64 visit_cookie; =20 #ifdef HAVE_RT_PUSH_IPI /* diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 296ff2acfd32..44093339761c 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -568,7 +568,7 @@ static int init_rootdomain(struct root_domain *rd) rd->rto_push_work =3D IRQ_WORK_INIT_HARD(rto_push_irq_work_func); #endif =20 - rd->visit_gen =3D 0; + rd->visit_cookie =3D 0; init_dl_bw(&rd->dl_bw); if (cpudl_init(&rd->cpudl) !=3D 0) goto free_rto_mask; --=20 2.48.1